Spatiotemporal dynamics of N and C biogeochemistry along a - - PowerPoint PPT Presentation

Spatiotemporal dynamics of N and C biogeochemistry along a wetland-stream sequence

Patrick Hurley1 | H. Maurice Valett1 | Marc Peipoch2

1University of Montana | 2Stroud Water Research Center | patrick1.hurley@umontana.edu

• 1. Lost Creek Dutchman Complex (LCDC)
• 2. Nutrient Patterns over Time and Space
• 3. Groundwater flowpaths drive N processing

Figure 2. Aerial photo of the LCDC as it flows towards the Upper Clark Fork River (UCFR). Figure 1. NO3-N (a) & DOC (b) concentration on a 23 km longitudinal

• gradient. NO3 increases dramatically

in reach II during both peak and base flows in contrast to DOC. DOC was higher during spring runoff and increased in reach III and IV. Figure 3. Long-term nutrient concentrations from the five main channel sites between Sept 2017 – Oct 2018. NO3 (a) is high from fall until peak runoff, then rebounds during the summer. NH4 (b) is low throughout the year. PO4 (c) and DOC (d) peak during spring runoff and return to background concentrations over the growing season.

REACH IV

1 km

N

Dutchman Cr

Upper Clark Fork River

Warm Springs

Figure 4. For all reaches, total change in NO3 load (∆LNO3) is driven by groundwater dissolved inorganic N inputs (LgwDIN). Removal of 1 outlier explains 30% of changes in ∆LNO3 over space and time (P=0.00064). Clustering of symbols suggest spatially- discrete nutrient process domains (NPD) based on biogeochemical character. Figure 5. δ18ONO3 and δ15NNO3

signatures from all

sites fall within the range for nitrification of NH4 from soil and/or septic sources and show spatial variability in N processing. Yellow circles are from above the wetland complex; purple triangles from Dutchman Cr and reach II zones; red diamonds are closest to the UCFR. Slopes between 0.5 and 1.0 typically indicate denitrification fractionation.

• 4. Contributions to the UCFR

NO3-N (kg d-1) DOC (kg d-1) Q (L sec-1)

11,431% 1,1447% 1,328%

Figure 6. LCDC inputs to the river are presented as % increase of NO3, DOC, and hydrologic load (Q), relative to the UCFR at Perkins Rd. Figure 7. Difference in CNO3 of the UCFR above and below the LCDC inputs.

Spatiotemporal dynamics of N and C biogeochemistry along a wetland-stream sequence

Patrick Hurley1 | H. Maurice Valett1 | Marc Peipoch2

1University of Montana | 2Stroud Water Research Center | patrick1.hurley@umontana.edu

• 1. Lost Creek Dutchman Complex (LCDC)
• 2. Nutrient Patterns over Time and Space
• 3. Groundwater flowpaths drive N processing

Figure 2. Aerial photo of the LCDC as it flows towards the Upper Clark Fork River (UCFR). Figure 1. NO3-N (a) & DOC (b) concentration on a 23 km longitudinal

• gradient. NO3 increases dramatically

in reach II during both peak and base flows in contrast to DOC. DOC was higher during spring runoff and increased in reach III and IV. Figure 3. Long-term nutrient concentrations from the five main channel sites between Sept 2017 – Oct 2018. NO3 (a) is high from fall until peak runoff, then rebounds during the summer. NH4 (b) is low throughout the year. PO4 (c) and DOC (d) peak during spring runoff and return to background concentrations over the growing season.

REACH IV

1 km

N

Dutchman Cr

Upper Clark Fork River

Warm Springs

Figure 4. For all reaches, total change in NO3 load (∆LNO3) is driven by groundwater dissolved inorganic N inputs (LgwDIN). Removal of 1 outlier explains 30% of changes in ∆LNO3 over space and time (P=0.00064). Clustering of symbols suggest spatially- discrete nutrient process domains (NPD) based on biogeochemical character. Figure 5. ∂18ONO3 and ∂15NNO3

signatures from all

sites fall within the range for nitrification of NH4 from soil and/or septic sources and show spatial variability in N processing. Yellow circles are from above the wetland complex; purple triangles from Dutchman Cr and reach II zones; red diamonds are closest to the UCFR. Slopes between 0.5 and 1.0 typically indicate denitrification fractionation.

• 4. Contributions to the UCFR

Dynamics of Biogeochemical Process Domains:

Wetland Influences on a Contaminated River

Patrick Hurley1 | H. Maurice Valett1 | Marc Peipoch2

1University of Montana | 2Stroud Water Research Center | patrick1.hurley@umontana.edu

SITE I SITE II SITE III SITE IV SITE V

• 1. Question & Hypothesis

Figure 3. a) LCDC discharge (m3/s), b) Seasonal and downstream trends in nitrate (kg NO3-N d-1); Dutchman Creek (red triangle) confluence in between sites I & II c) Nitrate loads at the base of each reach d) Ammonium & phosphate loads among reaches. Figure 2. Aerial photo of Lost Creek-Dutchman Complex (LCDC) – an identified source of inorganic nitrogen – as it flows towards the Upper Clark Fork River (UCFR).

Upper Clark Fork River 1 km

• 2. Nitrogen Sources to the UCFR

Q: H:

Figure 1. Longitudinal trends in nitrogen of the UCFR show reaches of significant gains.

Lost Creek-Dutchman Complex

• 3. Seasonal & Spatial Trends
• 4. Future Mass Balance Study
• Longitudinal sampling of the

Upper Clark Fork River (UCFR) identified Lost Creek-Dutchman Complex (LCDC) as a zone of substantial N contributions (yellow stars)

• Reaches may be nutrients donors,

transformers, conveyors, or removers.

• Segmented study reaches

(colored) provide a comprehensive assessment of the dynamics of each potential NPD within the LCDC

d. c.

• Hydrologic variation is associated with summer drought and

agricultural drawdown.

• Nutrient loads fluctuate with discharge and biologic influences
• Inorganic N loads predicted to be related to the seasonal

capacity for nutrient uptake by in-stream biota.

• Potential for buried peat-wetland to support large-scale

mineralization & nitrification and act as N donor

• Develop theoretical bases for NPD as important influences on catchment-

wide stream dynamics and biogeochemical function

• 6-month biogeochemical and hydrologic assessment using mass balance to

determine nutrient sources and sinks and characterize NPDs along a landscape-scale wetland-stream sequence

• Evaluate input & output nutrient loads across four spatially distinct reaches
• Quantify seasonal variability in NPD behavior
• Quantify total annual loads to UCFR to inform nutrient reduction efforts

How do nutrient process domains (NPDs)

characterize discrete biogeochemical zones that influence whole-stream nutrient budgets within linked aquatic ecosystems? Hydrologic, geomorphic, and biologic factors drive nutrient cycling and dictate dominant biogeochemical behavior that distinguish nutrient fates among NPDs.

b. a. 3.0 4.5 1.5 2012 2014 2016 2018 1 2 3 4 5 Q (m3/s) Site NO3-N (mg/L) 0.4 0.6 0.2

Oct 2017 Feb 2018 Apr 2018

10 20 30 40 60 100 140 Distance Downstream (km) NO3-N (mg/L) NH4-N (mg/L) PO4-P (mg/L)

1

2 3 4 5 Site 1 2 3 4 5 Site 0.2 0.1 NH4-N (kg/day) PO4-P (kg/d) NO3-N (kg/d) 8 6 4 2 20

Dutchman Creek

Lost Creek

NH4-N (µg/L) NO3-N (µg/L)

N

REACH I REACH III REACH IV

1 km

REACH II

Dutchman Cr

Upper Clark Fork River

Warm Springs

Figure 2. Aerial photo of the LCDC as it flows towards the Upper Clark Fork River (UCFR). Figure 1. NO3-N & DOC concentration

• n a 23 km longitudinal gradient. NO3

increases dramatically in reach II during both peak and base flows in contrast to DOC. DOC was higher during spring runoff and increased in reach III and IV.

• 1. Lost Creek Dutchman Complex (LCDC)